The present invention relates to a fuel injection pump associated with an internal combustion engine.
One of conventionally known fuel injection pumps is a so-called star type fuel injection pump which has a plurality of plungers disposed in radial directions with respect to a cam. A fuel pressurizing chamber is formed for each plunger. The plunger causes a pressing movement in response to rotation of the cam for pressurizing the fuel stored in the fuel pressurizing chamber. According to the star-type fuel injection pump, respective fuel pressurizing chambers send out the high-pressure fuel via their fuel feed passages. The fuel feed passages of respective fuel pressurizing chambers merge into a single fuel feed passage. The pressurized fuel is then supplied from the single fuel feed passage to a common rail.
The unexamined Japanese patent publication No. 2000-240531, corresponding to U.S. Pat. No. 6,289,875, discloses the accumulator type fuel injection pump which has a cylinder head for slidably supporting plungers which reciprocate in radial directions with respect to a drive shaft. This conventional fuel injection pump has a pipe joint member which is formed separately from the cylinder head. The pipe joint member is an intermediate joint member which holds or supports a high-pressure check valve attached to the cylinder head. The high-pressure check valve comprises a ball valve member and a spring accommodated therein. One end of the pipe joint member is inserted into a joint port of the cylinder head so as to fixedly holds or supports the check valve. The other end of the pipe joint member is connected to a fuel pipe of the common rail.
Recently, to improve the fuel consumption, downsizing of an engine body is earnestly required. Accordingly, the size of a fuel injection pump must be small. The screw size of a pipe joint member must be small too. This may force the pipe joint member to rotate together with the fuel pipe during a fastening operation of the fuel pipe. The cylinder head will be subjected to an excessive load which possibly causes deformation of the cylinder head and accordingly causes seizure of the plungers. Furthermore, there is the possibility that the pipe joint member may loosen when the pipe joint member rotates together with the fuel pipe. This will result in leakage of oil.
In view of the above-described problems, the present invention has an object to provide a fuel injection pump which is capable of preventing the pump housing from deforming and also preventing the pump components or members from seizing, thereby improving the reliability of fuel injection pump.
Another object of the present invention is to provide a fuel injection pump which is capable of eliminating the leakage of oil which may be caused when the pipe joint member is loosened.
Furthermore, another object of the present invention is to provide a fuel injection pump which has an optimized arrangement for facilitating the installation of fuel pipes to the pump housing.
In order to accomplish the above and other related objects, the present invention provides a fuel injection pump comprising a drive shaft and a cam rotating together with the drive shaft. A movable member, driven by the cam, reciprocates in accordance with rotation of the cam for pressurizing the fuel introduced in a fuel pressurizing chamber. The pressurized fuel is fed from the fuel pressurizing chamber to an accumulator via a fuel feed passage. A pump housing has the fuel feed passage formed therein. A pipe joint portion is integrally formed with the pump housing and is directly connectable to a piping member of the accumulator.
According to the arrangement of the fuel injection pump of the present invention, the pipe joint portion is integrally formed with the pump housing. Thus, it is possible to surely prevent the pipe joint portion from rotating together with the piping member of the accumulator during a fastening operation of the piping member of the accumulator. Even if the size of the pump housing is reduced, the pipe joint portion does not rotate. This prevents the pump housing from being subjected to an excessive load. Accordingly, it becomes possible to prevent the pump housing from deforming and also prevent the movable member from seizing. Thus, the reliability of fuel injection pump can be improved. Needless to say, no leakage of oil occurs because the pipe joint portion does not loosen.
It is preferable that the pipe joint portion has an external thread portion engageable with the piping member of the accumulator. Alternatively, it is preferable that the pipe joint portion has an internal thread portion engageable with the piping member of the accumulator.
This arrangement makes it easy to install the piping member after finishing the installation of fuel injection pump to the engine body. The time required for installing the piping member can be reduced. This realizes optimized pipe connection which causes no interference between the piping member and peripheral members. The degree of freedom is improved in the mounting of fuel injection pump.
Furthermore, it is preferable that the pump housing has a first opening connected to a piping member communicating with other pump chamber via an intermediate joint member which holds a check valve, and has a second opening directly connected to the piping member of the accumulator.
Moreover, it is preferable that the pump housing supports the movable member so as to allow the movable member to reciprocate in this pump housing.